JP2008175720A - Infrared sensor and infrared sensor array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturized infrared sensor having high detection sensitivity to infrared radiation of a wavelength of 20 μm or lower, especially about 10 μmd. <P>SOLUTION: An infrared sensor for detecting light incoming to an infrared detection section includes a substrate, a cavity section formed in the substrate, the rectangular infrared detection section supported by supporting legs on the cavity section, and a mirror disposed on the substrate along only one side of the infrared detection section. The light incoming to the mirror is reflected by the mirror and incomes to the infrared detection section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a miniaturized infrared sensor and infrared sensor array, and more particularly, to a thermal infrared sensor and an infrared sensor array that detect infrared rays having a wavelength of about 10 μm.

In a conventional infrared sensor, a condenser mirror having a plurality of through-holes for infrared incidence is fixed on a sensor array having an infrared light receiver so that the infrared receiver is surrounded by the condenser mirror to reduce the light receiving area. The detection sensitivity is improved by increasing it (see, for example, Patent Document 1).
In order to improve detection sensitivity, a microbolometer provided with a condensing mirror called a 3D horn antenna has also been proposed (see, for example, Non-Patent Document 1).
JP 2005-268660 A K. Kim et al .: “3D-feed horn antenna-coupled microbolometer”, Sensors and Actuators A 110 (2004) pp.196-205

  In an array type infrared sensor applied to an infrared camera, it is necessary to reduce the pixel formation region in order to increase the definition, increase the number of pixels, and reduce the size of the optical system. The pixel pitch is being reduced from the current 100 μm to the order of 20 μm. In such an infrared sensor, the length of one side of the substantially rectangular infrared detection unit is about 10 μm, and the length of one side of the opening of the condensing mirror surrounding the infrared light receiving unit is also about 10 μm.

  However, when such an infrared sensor is used for detection of infrared rays having a wavelength of about 10 μm, there is a problem that the detection sensitivity is not improved even if a condenser mirror is provided. On the other hand, as a result of intensive studies by the inventors, when the wavelength of infrared rays (detection wavelength) incident on the infrared sensor is approximately the same as the size of the opening, the infrared light that should pass through the opening is reflected, and the infrared It has been found that the amount of infrared rays incident on the detector is reduced and the detection sensitivity is lowered. That is, the inventors found such a problem in the process of increasing the definition of the infrared sensor, and completed the present invention to solve this problem.

  That is, an object of the present invention is to provide a miniaturized infrared sensor and infrared sensor array having high detection sensitivity even for infrared rays having a detection wavelength of 20 μm or less, particularly about 10 μm.

  The present invention is an infrared sensor that detects light incident on an infrared detection unit, a substrate, a cavity formed in the substrate, a rectangular infrared detection unit supported by a support leg on the cavity, and an infrared ray The infrared sensor includes a mirror provided on the substrate along only one side of the detection unit, and light incident on the mirror is reflected by the mirror and enters the infrared detection unit.

  Further, the present invention provides an infrared sensor including a substrate, a cavity formed in the substrate, and a rectangular infrared detection unit supported by a support leg on the cavity in two orthogonal directions included in the substrate. An infrared sensor array juxtaposed in an array, wherein a mirror is formed on the substrate along the infrared detector only in one of the two orthogonal axes, and the light incident on the mirror is reflected by the mirror. And an infrared sensor array that is incident on the infrared detection unit.

  As described above, the present invention can provide a miniaturized and high-definition infrared sensor having high detection efficiency even for infrared rays having a wavelength of about 10 μm.

  In addition, since the infrared sensor can be manufactured by a monolithic process, the manufacturing method can be simplified.

Embodiment 1 FIG.
FIG. 1 is a perspective view of an infrared detection device according to a first exemplary embodiment of the present invention, the whole being represented by 200. FIG. The infrared detection device has a substrate 7 made of, for example, silicon. On the substrate 7, a plurality of thermal infrared sensors (infrared detection elements) 100 are arranged in an array. Around the infrared sensor 100, an external circuit 210 for processing an electrical signal obtained from the infrared sensor 100 is provided.

  FIG. 2 shows the infrared sensor 100 according to the first embodiment. FIG. 2A is a plan view, and FIG. 2B is a cross-sectional view when FIG. 2A is viewed in the II-II direction. Indicates. The II-II direction corresponds to the II direction of FIG. In FIG. 2, four (2 × 2) infrared sensors 100 are shown.

  As shown in FIG. 2, the infrared sensor 100 includes a substrate 7 made of, for example, silicon. An insulator 5 made of, for example, silicon oxide is formed on the substrate 7 so as to be partially embedded in the substrate 7. The insulator 5 is formed so as to cover the wiring layer 6 formed thereon. The wiring layer 6 is formed of, for example, Al—Cu or the like from an aluminum alloy or aluminum. A hollow portion 8 is provided in the substrate 7, and an infrared detection unit 4 supported by the support legs 3 is provided thereon. Due to the heat insulating structure provided with the hollow portion 8, the light incident on the infrared detecting portion 4 is efficiently converted into heat.

  The infrared detection unit 4 has a rectangular shape, for example, and has a width (short side) of 20 μm or less, here about 10 μm, which is about the same as the detection wavelength of the infrared detection unit 4. The vertical width (long side) is larger than 10 μm. Further, as shown in FIG. 2A, for example, the support legs 3 are connected to the left and right sides of the infrared detection unit 4 and have a meandering shape. In the infrared sensor 100, since the support leg 3 is provided on the lateral side of the infrared detection unit 4, the incident light to this region is not detected. For this reason, the mirror 2 to be described later is formed so as to cover a part of the support leg 3 on the side of the infrared detection unit 4 so that incident light to this region can be detected.

The infrared detection unit 4 is made of, for example, a silicon diode, but may be formed of a bolometer thin film such as vanadium oxide, polysilicon, or amorphous silicon. The infrared detector 4 and the wiring layer 6 are connected by a wiring (not shown) provided on the support leg 3.
The jumper wiring, the connection wiring between the wirings 6, the connection wiring to the external circuit 210, etc. in the portion where the wiring 6 arranged in the vertical direction straddles the wiring 6 arranged in the horizontal direction are the same as those of the conventional infrared sensor. And is omitted here.

  On the insulator 5, a support 9 is provided so as to overhang the cavity 8, and the mirror 2 is fixed at a predetermined angle thereon. The mirror 2 has, for example, a laminated structure of a silicon oxide film and a platinum film. As shown in FIG. 2 (a), the mirror 2 extends in the vertical direction (vertical direction in FIG. 2 (a)) and is arranged in the horizontal direction, and is arranged in the horizontal direction (horizontal direction in FIG. 2 (a)). It is not provided so as to extend. As shown in FIG. 2A, the mirror 2 is preferably formed integrally with the plurality of infrared sensors 100 as a common mirror.

The angle of the mirror 2 is generally an angle at which light incident from the normal direction of the substrate 7 is reflected and irradiated to the infrared detection unit 4.
The mirror 2 is formed with a mirror support through-hole 2a to increase the strength and maintain a desired shape. However, when the mirror 2 is supported by the end of the array, such as in a small-scale array, etc. The mirror support through hole 2a may not be provided.

  In the first embodiment, the shape of the mirror 2 is a flat plate, but it may be a non-flat mirror 2 such as a curved surface. The same applies to the following second and third embodiments.

  In the infrared sensor 100, when detection light is incident on the infrared detection unit 4, light energy is changed to thermal energy in the infrared detection unit 4, and the temperature of the infrared detection unit 4 is changed. Along with this, for example, the physical property value of the infrared detecting unit 4 such as a resistance value changes, and incident light is detected by detecting this through a wiring (not shown) provided on the support leg 3. In the infrared sensor 100 according to the first embodiment, in addition to the detection light that is directly incident on the infrared detection unit 4, the incident light that is incident on the mirror 2 is also reflected and enters the infrared detection unit 4. That is, the area (aperture ratio) of the infrared detector 4 is substantially increased and the detection sensitivity of incident light is improved.

  As described above, when a condensing mirror having a length approximately equal to the detection wavelength (about 10 μm) is provided on one side of the opening, the infrared rays that should pass through the opening are reflected, and the detection efficiency is reduced. As in the infrared sensor 100 according to the first embodiment, the mirror 2 is formed in one direction without surrounding the infrared detection unit 4, so that the vertical direction (vertical direction in FIG. 2A) is infrared. Since the detection unit 4 occupies most of the light receiving region, there are few incident light components that are wasted, and there is no reduction in efficiency because the mirror 2 is not provided. Since the support leg 3 has a meandering shape and is arranged so as to sandwich the infrared detection unit 4, it is possible to group areas that cannot be detected in one infrared detection unit 4 and the infrared detection unit 4 adjacent in the lateral direction. Incident light is effectively detected by providing a mirror 2 in a part on the top. The mirror 2 may be formed in the entire region where the support leg 3 is formed. As shown in FIG. 2, when the width of the infrared detection unit 4 is about the same as the detection wavelength and the whole is covered, reflection of incident light becomes strong, and when it is more efficient to form only a part, The mirror 2 may be formed in a part of the region where the support leg 3 is formed. As described above, the incident light is incident on the infrared detector 4 and the infrared sensor 100 having high detection sensitivity can be obtained.

Next, a method for manufacturing the infrared sensor 100 according to the first embodiment will be described with reference to FIGS. This manufacturing method includes the following steps 1 to 4.
3 to 5, as in FIG. 2, (a) is a plan view of four (2 × 2) infrared sensors 100, (b) is a cross-sectional view thereof, and FIG. The same code | symbol shows the same or an equivalent location.

Step 1: As shown in FIG. 3, first, a substrate 7 made of, for example, silicon is prepared. Subsequently, an insulator 5 made of, for example, silicon oxide is formed so as to be partially embedded in the substrate 7. The insulator 5 is also formed so as to cover the wiring layer 6 made of, for example, an aluminum alloy formed thereon.
An insulating layer made of, for example, silicon oxide is formed on the surface of the substrate 7, and this is etched to form the support legs 3. In addition, the infrared detection unit 4 is formed in the center of the support leg 3 so that both sides are connected to the support leg 3. The infrared detector 4 is made of, for example, a silicon pn diode. Although not shown here, the infrared detector 4 and the wiring layer 6 are electrically connected by forming a wiring on the support leg 3.

Step 2: As shown in FIG. 4, an embedded sacrificial layer 10 made of, for example, polyimide is formed so as to cover the support legs 3 and the infrared detection unit 4. The surface of the buried sacrificial layer 10 has the same height as the surface of the insulator 5, and the surface of the insulator 5 is exposed from the buried sacrificial layer 10.
Subsequently, for example, a silicon oxide film is formed so as to cover the entire surface, and this is etched to form the support 9.

Step 3: As shown in FIG. 5, after forming a photoresist layer having a film thickness of about 20 μm, it is processed using a photolithography technique to form a mirror support 20 having a trapezoidal cross-sectional shape. In photolithography, an exposure method is used in which the intensity of exposure light is modulated so that the light intensity changes in the incident plane. Further, the mirror support through-hole 2a is formed using a photolithography technique.
Subsequently, for example, a silicon oxide film and a platinum film are formed on the mirror support 20 and then selectively removed to form the mirror 2. The mirror 2 is fixed to the support 9 at the lower part. In this step, it is possible not to form the mirror support through hole 2a.
In order to form the position of the mirror support 20 with high accuracy, it is preferable to use an existing high step lithography method such as a spray coating method of a photoresist or a long focus exposure method.

Step 4: The mirror support 20 and the buried sacrificial layer 10 are removed using oxygen plasma or the like, and then the substrate 8 is etched to form the cavity 8.
Thereby, as shown in FIG. 2, the infrared sensor 100 in which the infrared detecting unit 4 is supported by the support leg 3 on the cavity 8 and the mirror 2 is fixed on the support 9 is completed.

By using such a manufacturing method, as in a conventional infrared sensor, a substrate on which an infrared detector is formed and a condenser mirror are separately manufactured and bonded together (hybrid structure). The thickness of the substrate to be formed is as thin as several tens of μm, and the width is about 10 μm. In some cases, the substrate has a plurality of beams of several mm to several centimeters. The mirror 2 that was difficult to manufacture can be manufactured.
In addition, since the mirror 2 is formed on the substrate 7 on which the infrared detection unit 4 is formed using a photolithography technique (monolithic structure), the infrared detection unit 4 and the mirror 2 can be easily and accurately aligned. it can.

Embodiment 2. FIG.
FIG. 6 is a cross-sectional view of the infrared sensor according to the second embodiment, the whole being represented by 200, and is a cross-sectional view when viewed in the II direction of FIG. In FIG. 6, two infrared sensors 200 are shown.

In the infrared sensor 200, after the mirror support 20 having a trapezoidal cross section is formed in the manufacturing process 3 of the first embodiment, and the mirror 2 is formed on the mirror support 20, a difference such as RIE using the mirror 2 as a mask is formed. A mirror support 20 as shown in FIG. 6 is formed by isotropic etching.
Subsequently, the sacrificial layer 10 is removed by isotropic etching, and the cavity 8 is formed.
Thereby, the infrared sensor 200 shown in FIG. 6 is completed. Other manufacturing steps are the same as those of the infrared sensor 100 described above.

In the infrared sensor 200 according to the second embodiment, since the mirror support 20 is provided below the mirror 2, the support strength of the mirror 2 can be increased.
In particular, the infrared sensor 200 having such a mirror support 20 can be manufactured with a simple manufacturing process.

Embodiment 3 FIG.
FIG. 7 is a cross-sectional view of the infrared sensor according to the third embodiment, which is represented as a whole by 300, and is a cross-sectional view when viewed in the II direction of FIG. In FIG. 7, two infrared sensors 300 are shown.

  In the infrared sensor 300, the line-shaped mirrors 2 are provided on both sides of the infrared detection unit 4, and reflected light from the mirror 2 enters the infrared detection unit 4 from both sides of the infrared detection unit 4. By using such a structure, the infrared sensor 300 with high detection sensitivity can be obtained.

  The infrared sensor 300 is preferably applied when the area of the infrared detection unit 4 is relatively large because both sides are surrounded by the mirror 2.

It is a perspective view of the infrared rays detection apparatus concerning Embodiment 1 of this invention. It is the top view and sectional drawing of the infrared sensor concerning Embodiment 1 of this invention. It is the top view and sectional drawing in the manufacturing process of the infrared sensor concerning Embodiment 1 of this invention. It is the top view and sectional drawing in the manufacturing process of the infrared sensor concerning Embodiment 1 of this invention. It is the top view and sectional drawing in the manufacturing process of the infrared sensor concerning Embodiment 1 of this invention. It is the top view and sectional drawing of the infrared sensor concerning Embodiment 2 of this invention. It is the top view and sectional drawing of an infrared sensor concerning Embodiment 3 of this invention.

Explanation of symbols

  2 mirror, 3 support leg, 4 infrared detection part, 5 insulator, 6 wiring layer, 7 substrate, 8 hollow part, 9 support, 10 sacrificial layer, 20 mirror support, 100 infrared sensor.

Claims (7)

An infrared sensor for detecting light incident on the infrared detector,
A substrate,
A cavity formed in the substrate;
The infrared detection unit supported by a support leg on the cavity,
A mirror provided on the substrate formed so as to cover at least a part of the support leg along only one side of the infrared detection unit,
An infrared sensor characterized in that light incident on the mirror is reflected by the mirror and incident on the infrared detector. Including an opposing mirror provided on the substrate along the other side of the infrared detection unit facing the one side,
2. The infrared sensor according to claim 1, wherein light reflected by the mirror and the counter mirror is incident on the infrared detection unit sandwiched between the mirror and the counter mirror. 3. The pair of support legs is provided only on the one side of the infrared detection unit and the other side facing the infrared detection unit so as to sandwich the infrared detection unit. The described infrared sensor. The infrared sensor according to claim 1, wherein the wavelength of light detected by the infrared sensor is 20 μm or less, and at least one side of the infrared detection unit is 20 μm or less. An infrared sensor including a substrate, a cavity formed in the substrate, and an infrared detector supported by a support leg on the cavity is juxtaposed in an array in two orthogonal directions included in the substrate. An infrared sensor array,
A mirror is formed on the substrate along the infrared detector only in one of the two orthogonal axes, and the light incident on the mirror is reflected by the mirror and incident on the infrared detector. An infrared sensor array.   The infrared detection unit includes a counter mirror disposed so as to face the mirror with the infrared detection unit interposed therebetween, and the light reflected by the mirror and the counter mirror is sandwiched between the mirror and the counter mirror The infrared sensor array according to claim 5, wherein the infrared sensor array is incident on the part.   The said mirror and / or the said opposing mirror consist of a common mirror integrally formed with respect to the said at least 2 said infrared sensor arrange | positioned at the said 1 axial direction, The Claim 5 or 6 characterized by the above-mentioned. Infrared sensor array.

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